A number of devices used in mass spectrometry and other fields involve a high number of ion optical elements that must be manufactured and assembled with a great deal of precision. For example, devices such as time-of-flight reflectrons, time-of-flight accelerators, ion funnels, ion tunnels, ion mobility columns, ion mirrors, and so forth can comprise periodic structures formed by many electrodes which are separated from one another by insulating spacers.
FIG. 1 illustrates a prior art ion mirror 10 that includes a plurality of axially-aligned ring-shaped electrodes 12 that define an interior volume 14. Insulating spacers 16 are disposed between adjacent electrodes 12, and electric potentials are applied to the electrodes 12 by a controller 18 to generate an electromagnetic field within the interior volume 14, thereby influencing an ion beam passing therethrough. In the ion mirror 10 of FIG. 1, each electrode 12 must be individually machined from a solid piece of electrically-conductive stock material, such as stainless steel or nickel-plated aluminum. It can be very difficult and expensive to machine such materials with the requisite degree of accuracy. The difficulty and expense are compounded by the need to assemble a large number of discrete components with very tight tolerances.
In CORNISH et al., “Miniature Time-Of-Flight Mass Spectrometer Using A Flexible Circuitboard Reflector,” Rapid Communications in Mass Spectrometry 14, 2408-2411 (2000), the entire content of which is incorporated herein by reference, an ion reflector is constructed by depositing a series of thin-copper traces on a flexible circuit board substrate. The substrate is then rolled into a tube with the copper traces facing inward to form ring-shaped electrodes. One disadvantage with such a structure is that at least some of the ions passing through the ion reflector collide with the exposed substrate regions between the copper traces. Over time, this can lead to a buildup of electrical charge on said regions and to the production of corresponding electromagnetic fields, which can have an unintended and undesired influence on the ion beam passing through the reflector.
U.S. Pat. No. 6,316,768 to Rockwood et al., entitled “PRINTED CIRCUIT BOARDS AS INSULATED COMPONENTS FOR A TIME OF FLIGHT MASS SPECTROMETER,” the entire content of which is incorporated herein by reference, purportedly addresses this concern by coating the exposed regions of substrate with a partially conductive coating that provides a discharge path to ground. Although this technique is said to prevent charge buildup between electrodes, it adds additional complexity, time, and expense to the manufacturing process, and reduces the durability and lifespan of the finished device.
Accordingly, a need exists for improved ion optical elements and related methods of making and using the same.